Exposition of the Blessed Sacrament day and night in continuity, during which time pious persons take their turns uninterruptedly as adorers. As a rule the object of this perpetual adoration is, reparation for the outrages of men against a God of goodness. The practise dates probably from the 12th or 13th century, when periods of adoration were sometimes prescribed by kings in thanksgiving for signal victories, and in the 15th century there were adorations in petition or thanksgiving for some special favor. The Forty Hours devotion, begun in 1534, developed the general practise of perpetual adoration, which is the special object of many pious associations and religious congregations established since that date.